Ferns

Ferns look lovely in a stumpery, but there is surprisingly more to ferns that you might expect.

Fern fiddlehead (Kate Russell)

These plants have been around for over 350 million years, long before flowering plants, or angiosperms, made their appearance. Or dinosaurs, for that matter! Ferns are vascular plants that do not produce flowers or seeds. Instead, they reproduce using spores, similar to mushrooms and other fungi.

There are over 10,000 known fern species of fern [so far] and some species can live for 100 years. While some ferns are nearly microscopic, others can reach 80 feet in height.

Ferns in a stumpery (Kate Russell)

There is a group of ferns (Azolla) found predominantly in water and they do not look like any ferns you might see on land. One in particular, the mosquito fern, is able to fix atmospheric nitrogen the same way land-dwelling legumes do before going to seed.

Fern anatomy

Ferns have three basic parts: rhizome, fronds, and sporangia. Fern rhizomes come in three forms: erect, lateral, and vertical.  Erect rhizomes provide the solid base from which leafy fronds unfurl. Laterally growing, creeping rhizomes move above and below ground and may even climb trees. Vertical rhizomes often look more like the trunk of a tree.

Fronds are a fern’s leaves. The leaf stem, called a petiole when referring to other types of plants, is called a fern’s stipe. The flat blade of the frond is called a lamina. The lamina is often segmented into pinnae by short stems called rachides. When a frond first appears, it is tightly curled and called a fiddlehead or koru. Fronds perform photosynthesis and they provide support for a fern’s reproductive sporangia. 

Black, brown, or orange sporangia are the reproductive structures of ferns. If there are no sporangia present, the fern is sterile. Normally found on the underside of the fronds, spores are formed in the sporangia. A cluster of sporangia is called a sorus. In some cases, a flap of tissue, called the indusium, may cover the sori until the spores are mature.

Tree fern spores (Anca Mosoiu) CC BY-SA 3.0

Fern reproduction

Ferns are unique in their method of reproduction and they are the only plants with two distinct living stages. As each spore matures, it becomes a sporophyte. Sporophytes that land in hospitable environments grow into very tiny, short-lived plants called gametophytes. Gametophytes have two sets of reproductive organs: a female archegonia and a male antheridia. Fertilization can take place within the same plant or between two neighboring plants. This fertilization produces a new sporophyte that grows into an adult fern.

Edible ferns

While most ferns are not considered edible, they also tend to not be poisonous. There are some varieties of fern that are edible, such as:

• bracken (Pteridium aquilinum)
• cinnamon fern (Osmundastrum cinnamomeum)
• king fern (Ptisana salicina)
• licorice fern (Polypodium glycyrrhiza)
• ostrich fern (Matteuccia struthiopteris)
• royal fern (Osmunda regalis)
• vegetable fern (Diplazium esculentum)

As always, do not eat anything you are not sure to be safe.

Fern pests and diseases

Ferns are naturally resistant to most plant-eating insects. One edible fern in particular, Tectaria macrodonta, has a gene that was transferred to cotton plants, providing resistance against whiteflies! Foliar nematodes (Aphelenchoides fragariae) and soil borne nematodes (Pratylenchus) can sometimes be a problem.

Ferns are susceptible to diseases such as bacterial blight (Pseudomonas cichorii or P. gladioli), Pythium root rot, and Rhizoctonia blight. Infected plants should be discarded. Environmental problems, such as drought, which causes graying, and over-fertilization, which results in frond lobing and leaf tip burn, can be avoided with good cultural practices. This means investing in disease-free plants, using only as much fertilizer as recommended for each fern species, and avoiding overhead watering. 

If you have a moist, shady crevice in your garden, ferns might be just what you've been looking for!